Abstract: To reveal the soil particle size distribution characteristics of different underlying surfaces of Mu Us Sandy Land, we analyzed soil grain size composition, parameters and particle size distribution curves of different underlying surfaces (fixed sandy land, semi-fixed sandy land, shifting sandy land, and lowland) by collecting soil samples at 0-5, 5-10 and 10-20 cm depth. The results showed that soil sand content in sandy lands was nearly 90%, being 30% higher than that in lowland. The content of very fine sand and clay+silt was between 3% to 15%, being more than 25% lower than that in lowland. There was no significant difference in sand content among fixed, semi-fixed and shifting sandy land. The content of very fine sand and clay+silt of soil in fixed sandy land was 10%-15%, being more than 7% higher than that in semi-fixed sandy land and shifting sandy land. The mean size of soil particles was 2.22 Φ, the standard deviation was 0.86 Φ, and the skewness was 0.14, which means the particle size shows a skew-normal distribution and poor sorting ability. The grain size parameters of soil in sandy lands were smaller than that in lowland. The particle size of sand dunes with different fixed degrees was in an order of shifting and semi-fixed sand dunes < fixed sand dunes. The particle size interval of the saltation in sandy lands and lowland was 1-3.5 Φ and 1-6 Φ, respectively. The sorting of saltation in lowland was worse than that in sandy lands, while the sorting of suspension was better. There were significant differences in grain size characteristics of soil among different underlying surfaces in Mu Us Sandy Land. The results could provide a theoretical basis for guiding desertification combating by classification at different zones in semi-arid regions.

Key words: soil particle size, lowland, sandy land, Mu Us Sandy Land